[Patch v9 02/10] block: Generalize chunk_sectors support as boundary support

John Garry
2024-06-20T12:55:00Z

The purpose of the chunk_sectors limit is to ensure that a mergeble request
fits within the boundary of the chunck_sector value.

Such a feature will be useful for other request_queue boundary limits, so
generalize the chunk_sectors merge code.

This idea was proposed by Hannes Reinecke.

Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: John Garry <john.g.garry@oracle.com>
---
block/blk-merge.c | 20 ++++++++++++++------
drivers/md/dm.c | 2 +-
include/linux/blkdev.h | 13 +++++++------
3 files changed, 22 insertions(+), 13 deletions(-)

diff --git a/block/blk-merge.c b/block/blk-merge.c
index 8957e08e020c..68969e27c831 100644
--- a/block/blk-merge.c
+++ b/block/blk-merge.c
@@ -154,6 +154,11 @@ static struct bio *bio_split_write_zeroes(struct bio *bio,
return bio_split(bio, lim->max_write_zeroes_sectors, GFP_NOIO, bs);
}

+static inline unsigned int blk_boundary_sectors(const struct queue_limits *lim)
+{
+ return lim->chunk_sectors;
+}
+
/*
* Return the maximum number of sectors from the start of a bio that may be
* submitted as a single request to a block device. If enough sectors remain,
@@ -167,12 +172,13 @@ static inline unsigned get_max_io_size(struct bio *bio,
{
unsigned pbs = lim->physical_block_size >> SECTOR_SHIFT;
unsigned lbs = lim->logical_block_size >> SECTOR_SHIFT;
+ unsigned boundary_sectors = blk_boundary_sectors(lim);
unsigned max_sectors = lim->max_sectors, start, end;

- if (lim->chunk_sectors) {
+ if (boundary_sectors) {
max_sectors = min(max_sectors,
- blk_chunk_sectors_left(bio->bi_iter.bi_sector,
- lim->chunk_sectors));
+ blk_boundary_sectors_left(bio->bi_iter.bi_sector,
+ boundary_sectors));
}

start = bio->bi_iter.bi_sector & (pbs - 1);
@@ -588,19 +594,21 @@ static inline unsigned int blk_rq_get_max_sectors(struct request *rq,
sector_t offset)
{
struct request_queue *q = rq->q;
- unsigned int max_sectors;
+ struct queue_limits *lim = &q->limits;
+ unsigned int max_sectors, boundary_sectors;

if (blk_rq_is_passthrough(rq))
return q->limits.max_hw_sectors;

+ boundary_sectors = blk_boundary_sectors(lim);
max_sectors = blk_queue_get_max_sectors(rq);

- if (!q->limits.chunk_sectors ||
+ if (!boundary_sectors ||
req_op(rq) == REQ_OP_DISCARD ||
req_op(rq) == REQ_OP_SECURE_ERASE)
return max_sectors;
return min(max_sectors,
- blk_chunk_sectors_left(offset, q->limits.chunk_sectors));
+ blk_boundary_sectors_left(offset, boundary_sectors));
}

static inline int ll_new_hw_segment(struct request *req, struct bio *bio,
diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index 8a976cee448b..7d107ae06e1a 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -1188,7 +1188,7 @@ static sector_t __max_io_len(struct dm_target *ti, sector_t sector,
return len;
return min_t(sector_t, len,
min(max_sectors ? : queue_max_sectors(ti->table->md->queue),
- blk_chunk_sectors_left(target_offset, max_granularity)));
+ blk_boundary_sectors_left(target_offset, max_granularity)));
}

static inline sector_t max_io_len(struct dm_target *ti, sector_t sector)
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index e96ba7b97288..4ff5886d3ca4 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -912,14 +912,15 @@ static inline bool bio_straddles_zones(struct bio *bio)
}

/*
- * Return how much of the chunk is left to be used for I/O at a given offset.
+ * Return how much within the boundary is left to be used for I/O at a given
+ * offset.
*/
-static inline unsigned int blk_chunk_sectors_left(sector_t offset,
- unsigned int chunk_sectors)
+static inline unsigned int blk_boundary_sectors_left(sector_t offset,
+ unsigned int boundary_sectors)
{
- if (unlikely(!is_power_of_2(chunk_sectors)))
- return chunk_sectors - sector_div(offset, chunk_sectors);
- return chunk_sectors - (offset & (chunk_sectors - 1));
+ if (unlikely(!is_power_of_2(boundary_sectors)))
+ return boundary_sectors - sector_div(offset, boundary_sectors);
+ return boundary_sectors - (offset & (boundary_sectors - 1));
}

/**
--
2.31.1